Conventionally, the image forming apparatus, such as a copying machine, a printer or FAX (facsimile machine), in which an image is formed using an electrophotographic process, has been known. The image forming apparatus of this type includes a fixing device for fixing the toner image on the recording material by heating and pressing the toner image.
In the fixing device, a cleaning device for cleaning offset toner transferred onto a fixing roller (heating portion) is provided (see Japanese Laid-Open Patent Application Hei 6-194986 and Japanese Laid-Open Patent Application 2004-212409).
Further, as such a cleaning device, a type using a cleaning sheet of a winding-up type (hereinafter, referred to as a web) has been known. Further, the cleaning device using the web is provided with a means for detecting a remaining amount of the web. Then, when the remaining amount of the web is in a small (little) state, notification to the effect that exchange of the web is prompted is made.
Therefore, in the case where the cleaning device is constituted as a cleaning unit detachably mountable to the image forming apparatus so that the web can be exchanged, in order to maintain a predetermined positional relationship with an object to be cleaned, the cleaning unit may preferably be locked. Further, on the other hand, for maintenance such as exchange of the cleaning unit, the cleaning unit is also in an unlocked state.
Thus, in the case where a mechanism for locking/unlocking the cleaning unit is provided, there is a liability that after the exchange of the cleaning unit, the cleaning unit is kept in the unlocked state due to an operational error. In such a state, there is a liability that the cleaning device cannot achieve sufficient cleaning performance. Recently, it is required to not only avoid such a situation but also achieve the sufficient cleaning performance without inviting an increase in cost.